One of the key limitations to understanding the genetic basis of complex human disease is the availability of good models. The laboratory rat is one such model which has tremendous value because of intensely studied physiological, pathological and sequence similarities to humans. More than 1300 disease-related quantitative trait loci (QTL) have been mapped in genetic studies in the rat. There is a disconnection, however, in the rat research field between physiology and genetics because there are no efficient means to mutate and identify genes. We have been developing a new tool to close this technology gap. We are now building upon preliminary data showing that transposon insertional mutagenesis using the Sleeping Beauty (SB) transposon system can generate heritable mutations in the rat at a rate which is 50-fold more efficient than conventional methods. We believe that properties of SB transposition, specifically the tendency for transposons to jump to nearby sequences within a chromosome (local hopping), will allow us to target these regions for mutagenesis and dramatically accelerate disease gene discovery. Another powerful application of transposon mutagenesis is cancer gene discovery. In somatic cells of transgenic rodents, SB transposon insertional mutagenesis can drive tumor formation by the rare, but repeated mutation of cancer genes. We can use the transposon to find these cancer genes by studying their insertion sites in tumor DNA. We specifically propose to develop these two applications in parallel to model genetic disease by 1) developing multiple transgenic strains which have transposons in different regions of the genome to take advantage of local hopping for transposon mutgenesis within QTL regions and 2) develop the SB transposon system for somatic mutagenesis in the rat. We chose the Dahl salt-sensitive (SS) inbred rat strain as our model because it is at the forefront of cardiovascular research among many researchers and we have preliminarily characterized it as a new model for human breast cancer. We will combine the SS strain and SB transposon mutagenesis with decades of physiological and pathological characterization to create the disease models and discover the disease genes which are involved. Narrative: The key for researchers to develop diagnostic testing and treatments for complex human diseases like cardiovascular disease and cancer is finding the genes that are responsible. We use what we call `genetic model organisms'like rats to understand the pathology of different diseases and work hard to discover genes that are involved by mutating, or removing them, and determining what happens. We are developing a powerful new tool which is much more efficient at doing this in the rat so that we can accelerate research in many disease areas to improve the quality of life for all of us.